1. Field of the Invention
This invention relates generally to metal oxide hydrogen batteries and more particularly to metal oxide-hydrogen batteries which provide for withdrawal of heat generated during battery operation.
2. Background Art
Metal oxide hydrogen batteries and in particular nickel oxide hydrogen batteries are expected to play a prominent role in research and development for and the future production of electric vehicles.
Metal oxide hydrogen batteries have been proposed which provide electric power through introduction of hydrogen within an enclosed chamber. The enclosed chamber is necessarily contained within an outer pressure vessel because of the high pressures which are generated by the introduction of hydrogen from a storage capacity outside of the pressure vessel. Such a device is described in U.S. Pat. No. 5,162,171 issued to Jones.
Devices of this type require heat removal from the pressure vessel because the hydrogenation-dehydrogenation process which occurs during discharge and recharge of the batteries generates tremendous amounts of heat. Devices of this type comprise battery cells within the high pressure chamber and include a series of flat bodies or fins having flanges which abut a metal wall of the high pressure chamber. Heat generated by the cell is transferred through the metal bodies and through the flanges into the wall of the high pressure vessel and the high pressure vessel then dissipates the heat into the ambient environment.
Heat transfer efficiency of these types of devices necessarily depends upon the quality and amount of contact between the flanges of the fins and the walls of the pressure vessels. Consequently, some mechanism is required to overcome a number of problems. A major problem is to provide and maintain good contact between the flanges or fins and the outer wall. For example, the flanges must be discontinuous around the edge of the fins so as to enable the flanges to conform to outer vessel shells that may be slightly out of round. Moreover, other considerations such as expansion of the outer walls of the pressure vessel and of the flanges and fins during battery operation must be taken into account in designing these types of devices.
Another major consideration is cost. High pressure hydrogen batteries require a massive and structurally integral enclosing outer pressure vessel, as such batteries cannot operate without the vessel. Due to safety considerations, these outer pressure vessels must be very strong and are tested to pressures several times the maximum expected hydrogen pressure. Should the vessel have a structural flaw such as a weak spot or even a minuscule leak, there exists danger of hydrogen escape and possibly of accelerated hydrogen combustion. The risk of such an event for high pressure hydrogen is such that extraordinary, and extremely expensive, measures are necessary to avoid the possibility of a catastrophic event.
Another factor adding to the cost of high pressure hydrogen batteries is the inability to change the configuration of the outer pressure vessel. That is, predetermined sizes and shapes of pressure vessels may be available, but the design of any device utilizing a hydrogen battery of the high pressure type must necessarily take into account the size and shape of the battery and hydrogen source vessel. Although these may be to some extent customized for a specific need, such customization also incurs great expense.